Expansible mandrels and other similar connecting devices are known in the prior art. Some are generally cylindrical in shape, others are generally conical in shape.
In U.S. Pat. No. 3,576,336 to Uhlig, a force transmitting device is disclosed which includes a conical body section movable relative to a plurality of segmented wedge members arranged around the body section, the wedge members being so arranged to exert a retaining force on a cylindrical part to be retained within another cylindrical part. The wedge members presented a truncated conical external surface and are thus tapered externally as well internally.
Spahn, U.S. Pat. No. 2,601,419 teaches the use of a pair of spaced frusto-pyramidal members, each of which is received in an opposite end of plurality of segmented members, so that upon movement of the frusto-pyramidal members toward one another, the segmented members expand radially. Resilient means surrounding the segmented member retain them in assembled relationship.